Cleansing Agents

Table of Content

What are Cleansing Agents?

Cleansing agents includes detergents. It includes soaps and synthetic detergents. It helps to improve cleansing properties of water.

Soaps are detergents made up of sodium or potassium salts with long chain fatty acids. Fatty acids can be stearic acid, oleic acid etc. For example, salts containing sodium salts are formed by heating fat with aqueous sodium hydroxide solution. This process is known as saponification. Fatty acid esters are hydrolyzed to form soap which is obtained in colloidal form. Then sodium chloride is added to precipitate from the solution. The solution left after removing the soap contains glycerol, which is obtained by fractional distillation. Sodium and potassium soaps are soluble in water. Potassium soaps are softer than sodium soaps.

Soap formation Fig. 1. Soap formation

Types of soaps

All soaps are made up of boiling oils or fats with soluble hydroxide. Following are the types of soaps known-

Toilet soaps are mild soaps made from better quality fats and oils with less alkali. They are composed of sodium laureth sulphate and sodium palmitate. To make them more consumer attractive, color and perfumes are added to it.

Soaps that float in water are formed by beating tiny air bubbles before they got hardened.

Transparent soaps are made by dissolving soap in ethanol and then evaporate the solvent, that is, ethanol. They are composed of sodium salt of fatty acids, citric acid etc.

Medicated soaps are those soaps in which some medicinal component is present. Shaving soaps contain glycerol for immediate drying. Rosin gum is added for making shaving soaps. Sodium rosinate gives lather property to it.

Structure of sodium rosinate Fig. 2. Structure of sodium rosinate

Laundry soaps contain sodium rosinate, sodium silicate, borax and sodium carbonate.

Why do soaps do not work in hard water?

Hard water is a water with high mineral content. Calcium and Magnesium ions are present in hard water. They form insoluble soaps with when sodium and potassium soaps are dissolved in water. These insoluble soaps are ineffective against cleansing action. Hair washed with hard water also looks sticky.

Reaction between soap and hard water Fig. 3. Reaction between soap and hard water

Synthetic Detergents

These Detergents contain all the properties of soaps. But they can be used for both hard and soft water. Synthetic detergents are classified as follows:

Anionic Detergents

They are the sodium salts of sulphonated long chain alcohols or hydrocarbons. They form electrically negatively charged ions in solution. The anionic part is important for cleansing action. Alkyl hydrogen sulphates are formed by treating concentrated sulphuric acid with long chain alcohols and neutralized with alkali to form anionic detergents. These detergents are found in toothpaste and other household products.

Anionic detergent structure Fig. 4. Anionic detergent structure

Cationic Detergents

Detergents with positively charged ions as active ions are known as cationic detergents. They have important foaming and cleansing properties. They are generally quaternary ammonium salts of amines with chlorides, bromides, or acetates as ions. For example, Cetyltriethylammonium bromide.

Structure of cationic detergent Fig. 5. Structure of cationic detergent

Frequently Asked Questions(FAQs)


Q1: What is in a degreaser?

Sol. Chemicals which can dissolve insoluble substances, for example, from floors, machines etc are known as Degreaser. They are generally made from xylene and kerosene.

Q2: Is bleach solvent based?

Sol.  Yes, bleach is solvent based cleanser.

Q3: Is bleach an alkali or an acid?

Sol. Bleach is alkali in nature.

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Cleansing Agents

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